Carbon Fiber Barrel and Method for Making the Same

ABSTRACT

A carbon fiber composite reinforced gun barrel and a method for making the same. The composite barrel that includes an interference fit gas block sleeve and machined steel ferrule that seals the gas port provided through the laminate composite reducing the risk of pressure leakage and delamination. The disclosed method of winding a carbon fiber resin composite on a structure, such as a rifle barrel, produces, for a given layer, constant wind angles that are engineered for longitudinal stiffness throughout the length of a given layer. The engineered wind angles throughout the length of each layer of fiber minimizing sacrificial material for the benefit of optimal fiber orientations and wound fiber collation. Whereas the base layers are defined by hoop winding, the orientation angles of successive strata becomes progressively lower and lower until the outermost strata achieve the target orientation angle of approximately 3 to 5 degrees.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/619,419, filed on Jan. 19, 2018, which is incorporated herein in its entirety by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION 1. Field of Invention

The invention relates to a reinforced gun barrel. More particularly, it relates to a carbon fiber composite reinforced gun barrel and a method for making the same.

2. Description of the Related Art

In the field of carbon fiber and resin composites, due to the higher strength to weight ratio of carbon fiber over steel, numerous tools and structural components, such as concrete pilings, aircraft wings and fuselages, automotive applications, and sporting goods are increasingly substituting carbon fiber and resin composites for steel. In the target shooting and related ballistic arts, it is known that highly accurate barrels are typically, or traditionally, longer, more robust, often referred to as “bull barrels”, and, therefore, heavy. It is also known that as consecutive shots are fired from a weapon, the barrel becomes hot, because of the detonating, heated, and rapidly expanding gases that result from the detonation of the gun powder in a cartridge. As the temperature of the barrel increases, the steel barrel undergoes thermodynamic, or thermal expansion. This thermal expansion reduces the frictional contact between the projectile and the internal rifling in the barrel, reducing accuracy of the weapon as the temperature of the barrel increases. Moreover, it is also known that vibrations induced by shock loading the material, from the high pressures contained by the barrel, cause unpredictable trajectories of the projectile. These vibrations resonate down the barrel and echo within the material; and these vibrations have a slow decay time in a dense isotropic material such as steel.

It is known that carbon fiber composite materials exhibit the physical properties to enhance the characteristics of a more accurately shooting barrel by reducing the overall weight, stiffening the barrel in the longitudinal planes, and absorbing the above-described vibrations. In this regard, in a composite reinforced barrel, the dissimilar materials of the composite resonate at differing and higher, natural frequencies. This dissonance more quickly cancels the resonance of the vibrations, than in a dense isotropic material like steel. The higher frequencies reduce the amplitude of the oscillations, which is the primary contributor to a barrel's lack of control over the projectile. Another benefit of the carbon fiber composite material is its higher tensile strength and modulus, constraining the diameter of the bore during firing, yielding greater control over the projectile and resulting in less induced deflection of the projectile. Further, certain carbon fiber composites have a higher rate of thermal conductivity, or heat dissipation, and have a greater degree of thermodynamic dimensional stability.

There are known carbon fiber composite barrels in the art. For instance, U.S. Pat. No. 4,685,236, issued to May on Aug. 11, 1987, discloses a gun barrel constructed of an inner tubular liner of hard material forming the bore of the barrel and an outer jacket of carbon-fiber reinforced metal matrix material in which the fibers are helically wound about the liner. Degerness, in U.S. Pat. No. 6,889,464, published on Dec. 9, 2004, and issued on May 10, 2005, discloses a composite barrel in which a high thermal conductivity material is added to the resin to increase thermal conductivity of the composite. However, it is known in the shooting arts that certain weapon platforms, such as the AR platform, e.g. the AR-15 civilian variant of the M-16, and the AK platform, based on the Russian AK-47, divert gas from a fired cartridge, either directly as in the AR platform or indirectly via a piston, for the AK platform, to the bolt carrier in order to cycle the weapon. This gas is known to reach momentary pressures in the range of approximately 55,000 psi. With the known prior art composite barrels, there is a risk of this pressure leaking past the gas port and delaminating the composite material.

What is missing from the art is a composite barrel that includes an interference fit gas block sleeve and machined ferrule that seals the gas port provided through the laminate composite reducing the risk of pressure leakage and delamination. Accordingly, it is an object of the present invention to provide a composite barrel, for a weapon such as a rifle, that has improved thermal properties for more rapid cooling of the barrel, which in turn improves the ballistic accuracy of the weapon and that is lighter weight than a state-of-the-art non-composite steel barrel. The composite, i.e. carbon fiber reinforced, barrel of the present application has application in various length rifle barrels, including without limitation, long barrels, carbine length barrels, short-barreled rifles, commonly referred to as SBR's, and pistols.

A further object of the present invention is to provide a more efficient method of winding a carbon fiber resin composite on a structure, such as a rifle barrel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above-mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:

FIG. 1A is a schematic view of the method of applying a carbon fiber composite material to two rifle barrels that have been adjoined muzzle to muzzle in order to create mirrored winding angles from end-to-end for a given layer of windings;

FIG. 1B is a close-up view of the circled region in FIG. 1A;

FIG. 2A is a close-up, longitudinal cross-sectional view of the barrel, composite windings, gas block landing sleeve, and an exemplary embodiment gas port ferrule of the present invention;

FIG. 2B is a close-up, longitudinal cross-sectional view of the barrel, composite windings, gas block landing sleeve, and a further embodiment gas port ferrule of the present invention; and

FIG. 3 is a further longitudinal cross-sectional view of the composite barrel and gas block landing sleeve of the present invention; and

FIG. 4 is a partial cross-sectional view of the tool adapted for removably attaching the barrel mandrel to a spindle.

DETAILED DESCRIPTION OF THE INVENTION

It will be appreciated by those skilled in the carbon fiber art that carbon fiber, in combination with a liquid resin is applied either in hoop wraps, helical wraps, low angle (relative to mandrel axis) wraps, or a combination of layers of hoop wraps, helical wraps, and low angle wraps, in a winding process. High angle hoop wraps provide circumferential strength, while lower angle and helical wraps provide greater longitudinal and axial tensile strength. FIGS. 1-3 illustrate the method of producing an improved composite rifle barrel, (FIG. 1), and the composite rifle barrel, gas block landing sleeve, and gas port ferrule, (FIGS. 2 and 3), of the present invention. Referring to FIG. 1, two barrels 1 are adjoined muzzle to muzzle by a threaded fastener 2. It will be appreciated that fastener 2 adjoins the barrels 1 such that the barrels share the same longitudinal axis. It will be further appreciated that the fastener 2 will be removed and the barrels 1 separated after the winding process is concluded. During the winding process, the adjoined steel barrels become, in effect, a mandrel about which the carbon fiber and resin composite is wound. In an exemplary embodiment, a thermally conductive fiber, such as a pitch based fiber is used as primary reinforcement and is combined with, preferably, an ablative bismaleimide, (“BMI”), resin, such as, though not limited to Raptor Resins' BMI 2 resin. Further, a tool member 4 is secured to the breach ends of the barrels 1. Tool member 4, which in an exemplary embodiment is adapted to be engaged by either a Morse taper or a lathe chuck of the spindle of a winding apparatus 5, as will be readily understood by one skilled in the art. BMI resin is preferred due to its behavior at critically high temperature. Whereas some known composite resins, when exposed to critically high heat, soften, a BMI resin, exposed to critically high heat, becomes harder, smokes and becomes brittle, and as the composite cools, will crack. Both softening and embrittling would be considered failure modes by those skilled in the art. However, the ablative resin's tendency to embrittle and crack provides the user a visual indication that the composite has reached a critical performance limitation whilst offering a safer and less catastrophic failure mode.

Those skilled in the art of carbon fiber composites will recognize that during the winding process, the wind angles vary at the longitudinal ends of the winding as the delivery eye or roller on the carriage (not shown), which traverses horizontally in line with the axis of the rotating mandrel, reverses direction. However, it is an object of the present invention to have constant wind angles that are engineered for longitudinal stiffness throughout the length of a given layer. The adjoined muzzles and the tool members 4 at the breach ends of barrels 1 serve to extend the length of the mandrel such that the change in direction occurs well beyond the end of the muzzle end of the barrels 1 thus providing constant, engineered wind angles throughout the length of each layer of fiber minimizing sacrificial material for the benefit of optimal fiber orientations and wound fiber collation.

In an exemplary embodiment, the geometry of the combination of the barrel mandrel, and the tool members 4 allow low wind angles in a range of approximately 3 to 5 degrees for the outermost strata of windings. It will be appreciated by those skilled in the art, that in an exemplary embodiment the winding of the first layer 20 is hoop winding. Then, the orientation angles of successive strata 22 becomes progressively lower and lower until the outermost strata achieve the target orientation angle of approximately 3 to 5 degrees. And, as stated above, within each strata of windings, the engineered wind angle for that strata is constant for the length of the strata. And, the base strata, i.e. the strata directly overlying the barrel 1, is a hoop wind, chosen for its circumferential strength to strengthen and constrain the diameter of the bore.

As stated above, the first layer 20, or base strata of the windings is a hoop wind, which fills the contours of the surface of the steel. This is necessary because barrel 1 is turned on a lathe in a single point turning operation. In an exemplary embodiment, the surface of the barrel 1 has a roughened or textured surface to enhance the contact area between the steel in the core barrel 1 and the carbon fiber composite material jacketing it in order to provide for greater heat conduction from the relatively low thermal conductivity of the steel into the relatively very high thermal conductivity of the carbon fiber composite.

Upon completion of the winding and composite curing processes, an initial grinding process creates an approximately uniform outer diameter, (“OD”), profile by removing excess winding material at 8 a, 8 b, 10. Then, the barrels 1 are separated at the muzzle end and the tool members 4 can be removed from the breach ends. The final grinding can be accomplished, as will be understood by those skilled in the art, to achieve the desired profile and surface finish for the rifle barrel.

It will be appreciated by those skilled in the firearm arts that in direct impingement systems, such as the common AR15 rifle platform, there is provided a small gas port 32 in the barrel 1 that vents the expansion gases, that result from the detonation of the gun powder in a cartridge, with every shot. This gas travels through the gas block and gas tube into the receiver, where it powers the bolt carrier group and cycles the firearm's action to load the next round.

Referring to FIGS. 2A, 2B, and 3, the gas block landing sleeve and gas port ferrule of the present invention will be described in greater detail. A gas block landing sleeve 27, preferably constructed of a material suitable for facilitating adequately securing the gas port ferrule and sufficiently resisting wear from repeated mounting and dismounting of the gas block 38 and resistant to erosion from gun gasses, defines an annular sleeve. The gas block landing sleeve 27 engages the composite barrel in an interference fit. In this regard, the inner diameter, (“ID”), of the gas block landing sleeve 27 is equal to, or approximately 0.0005″ to approximately 0.001″ smaller than the outer diameter, (“OD”), of the selected portion of the composite barrel. The gas block landing sleeve 27 is then heated such that it expands by 0.001″ to approximately 0.0015″ and is then pressed into place where it cools forming a press fit, or interference fit. In order to further secure the gas block landing sleeve 27 to the composite, shallow, circumferential adhesive galleys 45 are machined into the composite 28 and filled with a selected adhesive. In an exemplary embodiment, the adhesive galleys are filled with a selected adhesive prior to pressing the heated gas block landing sleeve into place. In an exemplary embodiment, the adhesive galleys 45 are approximately 0.0015″ to approximately 0.003″ deep. Depending upon the desired profile of the composite barrel, a shoulder may be machined into the composite 28 at a selected location determined by the gas system dwell time of the rifle. In such a configuration, gas block landing sleeve 27 also includes a radial shoulder that engages the shoulder machined into composite 28.

Those skilled in the art of semi-automatic rifles will understand that high pressure, high velocity, and high temperature gas passes through the gas port 32 drilled through the composite 28 and barrel core 26. Composite 28 must be sealed off at the location of the gas port 32, and thus isolated from the gas port 32, in order to prevent the expansion gases, that result from the detonation of the gun powder in a cartridge, from leaching through the strata of composite 28 and creating a risk of delaminating the strata of composite 28. In order to seal the composite 28, a steel ferrule 30 having a longitudinal bore is provided that engages barrel core 26 and is sealed to gas block landing sleeve 27 thereby providing a duct through which the gases flow in the direction of arrow 24.

In an exemplary embodiment, ferrule 30 is stainless steel and has a conical taper 31 at an interior end 34. Taper 31 engages a chamfer 29 drilled into the barrel core 26 when the gas port 32 is drilled. In an exemplary embodiment, taper 31 has a slightly steeper angle than chamfer 29 so as to create a pressure seal 40 when ferrule 30 is pressed into the gas port 32.

When the gas port 32 is drilled through gas block landing sleeve 27, a countersink, or chamfer 33 is provided in gas block landing sleeve 27. This provides a space for a fillet weld 35 between ferrule 30 and gas block landing sleeve 27. To provide filler material for this fillet weld 35, the outer end of ferrule 30 is machined so as to provide a ridge 36 of excess material.

When ferrule 30 is press fit into the gas port 32 and welded to the gas block landing sleeve 27, a pressure seal 40 is formed, as discussed above. Also, in order to facilitate the seal and reduce backpressure at the pressure seal 40 between barrel core 26 and ferrule 30, thereby mitigating gas blow by, a divergent duct is formed between barrel core 26 and ferrule 30. This is accomplished by providing ferrule 30 with an interior diameter, (“ID”), that is in a range of approximately 0.005″ to approximately 0.010″ larger than the ID of the gas port 32 provided in barrel core 26. It will be appreciated that to further reduce back pressure at this joint, in a further exemplary embodiment, the channel in ferrule 30′ could be conical, opening upwards from approximately 0.083″ to approximately 0.125″ in the direction of the gas block 38, as illustrated in FIG. 2B, instead of being cylindrical as illustrated in FIG. 2A. Such a divergent duct would act to thrust such a ferrule into its seat further promoting said seal.

Referring to FIG. 4, tool member 4 will be described in greater detail. Tool member 4 includes a first distal end 55 adapted to be received by either a Morse taper or a lathe chuck. A second distal end 60 includes a threaded bore 65 adapted to be threaded onto the threaded member of the barrel disposed at the breach end of the barrel. A drafted, or tapered shaft 70 is disposed between the first distal end 55 and the second distal end 60 and defines the body of tool member 4. As described above, the length of tool member 4 at the breach ends of barrels 1 assists in extending the effective length of the mandrel such that the change in winding direction occurs beyond the end of the breech end of the barrels 1 thus providing constant, engineered wind angles throughout the length of each layer of fiber.

As a final step, and in an exemplary embodiment, a 10-30 micron abrasive paper provides a final polish; and any grinding residue that might be bedded in the surface is blown out with forced air. A fine coat of a high temperature polymer, blended wax is applied in order to protect the user from any skin irritating carbon fibers that might be on the surface and also to protect the end fibers that are on the surface of the composite material.

While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept. 

Having thus described the aforementioned invention, what is claimed is:
 1. A carbon fiber resin composite reinforced gun barrel having a reinforced gas port, said carbon fiber composite reinforced gun barrel comprising: a barrel defined by a steel barrel core having a longitudinal bore adapted for the passage of a projectile; a carbon fiber resin composite wrapped around said barrel core, said carbon fiber resin composite being wrapped in multiple strata wherein orientation angles of successive strata become progressively lower; an annular gas block landing sleeve carried by said barrel and engaging said barrel in an interference fit; a gas port drilled in a selected location through said barrel core, said gas block landing sleeve, and said strata of said carbon fiber resin composite, said gas port adapted for providing fluid communication between said longitudinal bore of said barrel and said gas block, said gas port including a chamfer proximate interior an interior end of said gas port; a gas port ferrule disposed through said gas port, said gas port ferrule having a longitudinal bore and further having a conical taper disposed at an interior end said conical taper adapted to form a pressure seal with said chamfer, said gas port ferrule being adapted for preventing said expansion gases from leaching through said strata of carbon fiber resin composite; and a gas block carried by said barrel and secured to said annular gas block landing sleeve.
 2. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein an innermost stratum of said carbon fiber resin composite winding is defined by high angle hoop wraps and a selected angle of outermost strata of said carbon fiber resin composite winding is defined by low angle helical wraps.
 3. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 2 wherein said outermost layers of strata of said carbon fiber resin composite windings have low wind angles in a range of approximately 3 to 5 degrees.
 4. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein said gas block landing includes a chamfer and further wherein said gas port ferrule is secured to said gas block landing sleeve by a fillet weld.
 5. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein said ferrule has an interior diameter that is in a range of approximately 0.005″ to approximately 0.010″ larger than an interior diameter of said gas port thereby forming a divergent duct.
 6. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein said longitudinal bore of said gas port ferrule is conical.
 7. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein said longitudinal bore of said gas port ferrule is cylindrical.
 8. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein said gas port ferrule is composed of steel.
 9. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 1 wherein said gun barrel further comprises circumferential adhesive galleys provided on said carbon fiber resin composite adjacent to said gas block landing sleeve adapted for receiving a selected adhesive for further securing said gas block landing sleeve to said carbon fiber resin composite, wherein said circumferential adhesive galleys are approximately 0.0015″ to approximately 0.003″ deep.
 10. A carbon fiber resin composite reinforced gun barrel having a reinforced gas port, said carbon fiber composite reinforced gun barrel comprising: a barrel defined by a steel barrel core having a longitudinal bore adapted for the passage of a projectile; a carbon fiber resin composite wrapped around said barrel core, said carbon fiber resin composite being wrapped in multiple strata wherein orientation angles of successive strata become progressively lower; an annular gas block landing sleeve carried by said barrel and engaging said barrel in an interference fit; a gas port drilled in a selected location through said barrel core, said gas block landing sleeve, and said strata of said carbon fiber resin composite, said gas port adapted for providing fluid communication between said longitudinal bore of said barrel and said gas block, said gas port including a chamfer proximate interior an interior end of said gas port, wherein said ferrule has an interior diameter that is in a range of approximately 0.005″ to approximately 0.010″ larger than an interior diameter of said gas port thereby forming a divergent duct; a gas port ferrule disposed through said gas port, said gas port ferrule having a longitudinal bore and further having a conical taper disposed at an interior end said conical taper adapted to form a pressure seal with said chamfer, said gas port ferrule being adapted for preventing said expansion gases from leaching through said strata of carbon fiber resin composite, wherein said gas block landing includes a chamfer and further wherein said gas port ferrule is secured to said gas block landing sleeve by a fillet weld; circumferential adhesive galleys provided on said carbon fiber resin composite adjacent to said gas block landing sleeve adapted for receiving a selected adhesive for further securing said gas block landing sleeve to said carbon fiber resin composite, wherein said circumferential adhesive galleys are approximately 0.0015″ to approximately 0.003″ deep; and a gas block carried by said barrel and secured to said annular gas block landing sleeve.
 11. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein an innermost stratum of said carbon fiber resin composite winding is defined by hoop winding.
 12. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein outermost layers of strata of said carbon fiber resin composite windings have low wind angles in a range of approximately 3 to 5 degrees.
 13. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein a wind angle of each said stratum of carbon fiber resin composite wound around said barrel core is an engineered wind angle that is constant for a length of said stratum.
 14. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein said longitudinal bore of said gas port ferrule is conical.
 15. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein said longitudinal bore of said gas port ferrule is cylindrical.
 16. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein said gas port ferrule is composed of steel.
 17. The carbon fiber resin composite reinforced gun barrel having a reinforced gas port of claim 10 wherein said gun barrel further comprises circumferential adhesive galleys provided on said carbon fiber resin composite adjacent to said gas block landing sleeve adapted for receiving a selected adhesive for further securing said gas block landing sleeve to said carbon fiber resin composite, wherein said circumferential adhesive galleys are approximately 0.0015″ to approximately 0.003″ deep. 